Estimation of l-5-hydroxytryptophan in rat serum and Griffonia seed extracts by liquid chromatography-mass spectrometry

The application of liquid chromatography-mass spectrometry (LC-MS) was investigated for the analysis of l-5-hydroxytryptophan (5-HTP) in rat serum. The chromatographic elution was carried out using C18 column (YMC, 250 mm × 2 mm, 5 μm) with a mobile phase water: acetonitrile (93:7, v/v). Quantitative analysis was performed by negative ion mode using selective ion monitoring (SIM) method with electrospray ionization interface. The serum samples were de-proteinized with acetonitrile. The limit of detection (LOD) and limit of quantification (LOQ) in the serum was found to be 2 and 6 ng and calibration curve ranging from 5 to 17 ng μl−1 showed to be linear with correlation coefficient 0.994 ± 0.0006. Within-day and day-to-day reproducibility were 0.39-0.44% and 0.66-1.67%, respectively and the recoveries of 5-HTP in the serum were 94.65-95.46%. The method developed was also found to be applicable for the analysis of Griffonia simplicifolia seed extracts and dosage forms with LOD and LOQ, 0.02 and 0.05 ng, respectively and linearity range 3-20 ng μl−1 with a correlation coefficient of 0.9992 ± 0.0004. The recoveries in the extracts were 97.00-100.20% and %R.S.D. of the intra- and inter-day precision was found to be 0.27-1.29% and 0.35-1.12%.